1. Field of the Invention
The invention relates to a cylinder; in particular, to an oil hydraulic cylinder and a spindle thereof provided with a surface protecting coat.
2. Description of Related Art
The conventional oil hydraulic cylinder has a cylinder body and a spindle received in the cylinder body. The spindle is movable in the cylinder body, and the spindle rubs against the inner wall of the cylinder body when the spindle moves in the cylinder body. Thus, the spindle needs high abrasion resistance and high strength, so the spindle is usually integrally formed by a material having high abrasion resistance and high strength.
However, the portion of the spindle rubbing against the cylinder body is a small part of the spindle, and the material of the entire spindle needs to be chosen to satisfy requirements for a small part of the spindle, such that the cost of the spindle cannot be decreased. Moreover, when the spindle is worn out, the entire spindle must be thrown away, creating a wasteful situation.
To achieve the abovementioned improvement, the inventors strive via industrial experience and academic research to present the instant disclosure, which can provide additional improvement as mentioned above.